Buy a bank of batteries and a Charge/Inverter, of the type that is used in BIG boats.. You know, where you plug into Shore-Power and charge batteries and then go to sea and run your fridge from the batteries or a generator.
The idea was to charge the batteries in OFF-PEAK hours at 8c and then run some refrigerators for the rest of the day.
Well the initial figures are in...

To run the fridges direct from house power, used 2.97Kwh and with an estimated cost of 61c.
To run the fridges from Battery system, used 8.1Kwh and with a real cost of 65c.
Whilst I will be experimenting more, it is clear that as far as cost is concerned - it's break even (excluding capital costs), and that using the battery system , involved dramatic inefficiency.. ie 8kwH to give back 3KwH.
I must say that I was expecting about 70>80% efficiency in the charge/invert process.
I think that the real issue is the efficiency of the "Chinese Inverter/Charger".. eg. Floating the batteries required .25KwH, and this quickly adds up. Unsurprisingly, the Inverter Manufacturer gave no figures for Charge and Invert efficiency.
My next phase will be to try and secure a recognised brand device, and see how it's efficiency pans out.
ie either an integrated 48V Charger/Inverter, or separate components.
Anyone in Sydney got a 48V charger for loan..?
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